Hair dyes and paraphenylenediamine allergy

This article has been translated from Finnish to English by Semantix. You can find the original article at the web adress

Current hair dye treatments can be roughly classified in temporary, semi-permanent and permanent, as well as plant-based treatments. Temporary or wash-out dyes are water-soluble acid colours or pigments that form a colour layer on the surface of the hair and are washed out in 1 or 2 washes. The non-oxidative hair dyes used in semi-permanent colour treatments do not penetrate deep into the hair, and they usually resist 4–6 washes. The permanent hair dye products and the so-called demi-permanent colours are oxidative hair colours that consist of colour precursors and oxidizing agents containing hydrogen peroxide (developer). Permanent hair dye provides a good coverage for grey hair and is resistant to shampoo washing, but the colour will have to be reapplied every 6 weeks due to new hair growth.

Paraphenylenediamine (p-Phenylenediamine) is a colourant which is primarily used to produce black and other dark colours. All oxidative permanent hair dyes use p-Phenylenediamine or its derivatives. Darker coloured dyes contain the highest amounts of colour precursors, but permanent light colours also contain p-Phenylenediamine or its derivatives. They are also found in permanent dyes used by professionals to colour eyelashes and eyebrows. In the cosmetics’ product information (permanent dyes used to colour hair, eyelashes and eyebrows), paraphenylenediamine is indicated as p-Phenylenediamine. In chemical labels and safety data sheets, paraphenylenediamine can be identified with the CAS Registry Number 106-50-3.

The most common health hazard caused by hair dyes is allergic contact dermatitis, which can also be caused by paraphenylenediamine. The mildest symptoms associated with an allergic reaction include slight itching a few days after dyeing the hair. In more severe cases, the symptoms can include swelling and irritation of the face and head area, and the eyelids can swell so much that the eyes close and they can be extremely itchy. Later, the skin might leak fluid and become flaky for a couple of weeks. A severe allergic reaction may even require hospitalisation. Dermatologist can diagnose contact dermatitis by making a series of epicutaneous patch tests. Allergic contact dermatitis is a lifelong condition. 

A person allergic to paraphenylenediamine should avoid the use of permanent hair, eyelash and eyebrow colours. A person allergic to paraphenylenediamine may also get a rash from permanent and demi-permanent hair dyes that do not contain paraphenylenediamine but its derivatives. The INCI names of the most commonly used derivatives are Toluene-2,5-diamine, 4-amino-2-hydroxytoluene and p-Aminophenol. Paraphenylenediamine and its derivatives are also used in the dyeing of leather and fur. Azo dyes, whose composition is similar to that of paraphenylenediamine, are used for textile dyeing. Sometimes these textile dyes may cause a rash to people who get severe allergic reactions from paraphenylenediamine. 

Lawsonia inermis plant is the source of henna extract which is used to dye hair and skin. The plant contains a dye named lawsone (2-hydroxy-1,4-naphthoquinone). Henna hair dye is suitable for persons who are allergic to paraphenylenediamine. Henna extracts can cause an immediate allergic reaction and, as a result, asthma and rhinitis. On the skin, it can cause contact urticaria. However, henna allergy is rare. 

Maria Pesonen
M.D., Specialist in Dermatology and Allergology
Finnish Institute of Occupational Health